1. Field of the Invention
The present invention relates to an electric connection box for automotive electrical wiring and, more particularly, to an electric connection box of such a construction that water that has entered the connection box and dropped onto an inside bottom surface can easily be drained from the inside bottom surface to prevent its accumulation between a bus bar circuit of the bottom layer and the inside bottom surface of the box which is likely to cause current leakage to occur in the bus bar circuit of the bottom layer.
2. Description of the Prior Art and Problem
An electric connection box, such as a junction box and a relay box, generally has the constitution as shown in FIG. 5.
In this drawing, numeral 1 denotes a bus bar circuit board with bus bar circuits 2 arranged on both sides, and numeral 3 indicates a surface cover provided with a connector housing portion 4 which is apertured for connection of relays and others with the outside thereof.
Tab terminals 5 or 5A are installed on the bus bar circuit 2 of the bus bar circuit board 1, projecting out upwardly or downwardly of the bus bar circuit board 1.
The tab terminals 5 are inserted in the apertured connector housing portion 4 formed in the surface cover 3 set on the bus bar circuit board 1, or the tab terminals 5A are inserted in a connector housing portion 9 provided in the box body 6a. (See FIG. 6.)
The surface cover 3 and the bus bar circuit board 1 are housed inside the box body 6, and a waterproof cover 7 is installed at the top opening of the box body 6.
FIG. 6 shows the surface cover 3 and the bus bar circuit board 1 which are housed inside the box body 6, with bus bar circuits 2A and 2B arranged on the upper and lower surfaces of the bus bar circuit board 1.
In the connector housing 4 mounted on the surface cover 3 extend the tab terminals 5 which are mated with female terminals 8 are inserted.
Therefore, terminal housing chambers 4a of the connector housing 4 are in communication with the outside thereof through the connector housing portion 4 in the vertical direction. Through this apertured connector housing portion 4, water (or water vapour) can enter the inside via the terminal housing chamber 4a in the direction of the arrow C, and furthermore can drop into a hole 1a provided in the bus bar circuit board 1 through which the tab terminals 5 are disposed, gathering on the inside bottom 6a of the box body 6. Thus water droplets will be formed between the bus bar circuit 2B of the bottom layer and the inside bottom surface 6a.
Also in a spacing between both edges of the surface cover 3 and the inside wall surface, water (or water vapour) is likely to enter as indicated by the arrow D in FIG. 6. Most of the water flows down along the inside wall surface of the box body 6, being drained out at the drain port 6b provided at the corner area where the inside wall surface and the inside bottom surface 6a meet. A part of the water, however, enters a spacing between the bus bar circuit 2B and the inside bottom surface 6a, accumulating thereat.
Particularly in an engine compartment of automobiles, it is very likely that rain water will enter and that sweating will be caused by substantial changes in temperatures, resulting in the water entrance into the connection box as described above.
Also as shown in FIG. 7, the spacing S between the bus bar circuit 2B of the bottom layer and the inside bottom surface 6a is less than the height of water droplets G caused by the surface tension of the water droplets, and the water droplets G, therefore, will be confined between the bus bar circuit 2B and the inside buttom surface 6a, easily accumulating therein because of their frictional force. In this state, the water droplets G will become extremely difficult to drain.